The present invention relates generally to metallic particles and more particularly, to a plasma-based method of producing a narrow distribution of spherical, metallic microparticles from smaller metallic nanoparticles.
The standard technology for producing aluminum particles in the 1-10 micron size diameter range, which may be optimal for metallic paints, involves converting larger metallic particles into smaller ones by wet the ball milling of the larger particles. Wet ball milling is an inefficient method of providing particles in this size range because only about 20% of the particles produced by wet ball milling are less than 10 microns and this minor fraction must be physically separated from the rest of the wet-ball milled product. A more efficient method for producing metallic particles in the optimal size range remains desirable.
Therefore, an object of the present invention is to provide an efficient method for producing high purity metallic particles of an optimal size range.
Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.
In accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention includes method for producing metallic particles from smaller metallic nanoparticles. The method includes generating an aerosol of precursor solid metallic nanoparticles, generating a non-oxidizing plasma having a hot zone with a temperature sufficiently high to melt the precursor nanoparticles and directing the aerosol into the hot zone. In the hot zone, the precursor nanoparticles melt, collide, join, spheroidize and become larger molten, spherical metallic particles. The larger, molten, spherical metallic particles are directed away from the hot zone so that they cool and solidify to form solid, spherical, metallic particles that are larger than the precursor nanoparticles.